TW201307056A - Polyamide-sheathed structural steel tubes for offshore structures - Google Patents

Abstract

The foundation structure of an offshore structure, for example of an offshore wind energy system, is composed of steel tubes sheathed by an extruded layer made of a polyamide moulding composition. This simultaneously ensures both good protection from corrosion and good protection from mechanical effects, giving the foundation structure markedly prolonged lifetime.

Description

Structural steel pipe with polyurethane sheath for offshore structures

The present invention relates to the use of a structural steel pipe having a sheath formed of an extruded layer made of a polyamide-molded composition in an offshore structure.

The offshore structure establishes a fixed structure offshore in the high seas. Examples of such offshore structures are wind energy systems, drilling platforms and lighthouses. The pipeline is not an offshore structure for the purposes of the present invention.

The basic structure of the offshore structure is the area that supports the actual base unit. In the case of a wind energy system, the infrastructure supports a tower of turbines and rotors. In the case of a drilling platform, the infrastructure supports a platform comprising an upper structure. In the case of a lighthouse, the infrastructure supports the tower, and if there is a light, it also supports the light. The infrastructure is under water, in the intertidal zone, in the surf zone or sometimes in the aerosol zone. The infrastructure consists of the basic elements that anchor it to the seabed.

Due to the planned expansion of wind energy, a large number of offshore wind energy systems are planned to be built in the North Sea and other seas and lakes in the coming years. The mechanical system of the offshore wind energy system consists entirely of the following components: turbines, rotors, towers and infrastructure.

The construction of the foundations of such systems on the water bed at locations over 100 km from the coast requires special structural elements that are quite different from the onshore sector. Some areas of such complex structural elements, such as single piles, sleeves Foundation piles, tripod piles, and triple piles are exposed to high static loads, and especially dynamic loads, as well as high levels of corrosive attack. Depending on the state and depth of the particular location being discussed, the factors that must be considered are the 50-year wave and the tidal range. Other factors that must be considered are intense UV radiation, salt water spray, aerosols, aerosols, temperature changes, mechanical loads, mollusks and other biological settlements, as well as mechanical erosion associated with animal organisms, as well as from animal organisms and other marine life. Chemical attack caused by excretion or secretion. These structural elements use steel pipes which may have a hermetic seal or may have a concrete fill for corrosion protection. In addition, there may be wires or other supply lines through the structural steel tubes.

To date, structural steel pipes required for structural elements have been designed with wall thicknesses significantly greater than (up to 25%) just the required thickness and using conventional coating materials for corrosion protection here, most of which are epoxy It is based on the substrate or polyurethane. These coating material systems do not provide any special protection against mechanical loads.

WO 2009/027429 discloses the use of a metal tube having a sheath formed with a layer of polyimide to produce a pipe without any grooves or sand beds. WO 2010/094528 discloses the manufacture of pipes laid in water using metal pipes with a sheath formed of an extruded layer made of a polyamide molded composition. However, in both cases, the tubing is not exposed to a combination of mechanical loads, corrosive attacks, and UV attacks that are typical in the present invention and include, for example, severe wave impact.

The present invention is based on the object of providing structural steel pipes for the basic structure of offshore structures which provide protection against mechanical loads and protection against corrosion and UV radiation more effectively than the related pipes known to date. .

The use of a steel tube with a sheath formed from an extruded layer of a polyamide-molded composition for the incorporation into the structure of an offshore structure is achieved for such purposes and other purposes as apparent from the application documents.

The offshore structure is preferably an offshore wind energy system, a drilling platform or a lighthouse.

The basic structure of the offshore wind energy system is the structure of the supporting tower. It extends from the base element anchored to the seabed and continues through the underwater structure until the point at which the tower begins, which may be higher than the still water surface.

The type of infrastructure used is as follows: The single pile structure consists of a hollow cylindrical pile. Single piles are used in many European offshore wind parks; they are suitable as a basis for water depths of up to about 20 meters. The installation of single piles is easy and quick; however, the construction requires extremely heavy piling equipment.

The telescopic pile is a steel skeleton similar to the structure used in conventional electric pylons. The pile anchors the four feet of the telescopic pile in the seabed. In the petroleum industry, the structure of the telescopic pile has proven successful for relatively deep waters. The skeletal structure can save 40 to 50% of the steel compared to a single pile. Therefore, this structure increases the planned cost relatively only slightly when the structure is used in deeper waters. Since individual structural components are relatively small, they are easy to manufacture and can be easily transported and installed.

The structure of the tripod pile is composed of the feet formed by three steel pipes. And the central pipe system is stacked on the center of the tripod pile. The legs of the tripod pile can be placed on one pile or on a plurality of piles. For piling, a centering sleeve is placed at the apex of the formed equilateral triangle. There are horizontal struts that connect the pile to the other piles, and the piles are attached to the central tube using diagonal struts. The central tube is not directly bonded to the seabed. Since a steel pipe having a relatively small diameter is used here, the tripod pile can be used for waters deeper than 20 meters.

The tripod base pile involves the modification of a tripod base using four feet instead of three feet. This results in an increase in the base stiffness in very deep waters.

The three-base pile consists of three steel columns anchored under water. The tripod pile structure is superposed on the steel columns above the water surface. According to the manufacturer's information, the three-pile foundation is suitable for waters with a depth of 25 to 50 meters.

Such structural elements are described, for example, in the following publications: Fundamente für Offshore-Windenergieanlagen [Foundations for offshore wind energy systems], Deutsche Energie-Agentur GmbH, Issue 12/09 - Florian Biehl, Kollisionssicherheit von Offshore-Windenergieanlagen [Collision safety of Offshore wind energy systems], Stahlbau, Vol. 78(6), pp. 402-409 (2009);- K. Lesny, W. Richwien (Editors), Gründung von Offshore-Windenergieanlagen - Werkzeuge für Planung and Bemessung [Foundations for Offshore wind energy systems - tools for design and dimensioning], VGE Verlag Glückauf 2008, ISBN: 978-3-86797-035-8;- DE 103 10 708 A1.

The polyamines which can be used according to the invention can be produced from a combination of diamines and dicarboxylic acids, from ω-amino carboxylic acids or from corresponding internal decylamines. In principle, it is possible to use, for example, polyamines such as PA46, PA6, PA66 or copolymerized decylamines derived from units of terephthalic acid and/or isophthalic acid (the formula used) For PPA). In a preferred embodiment, the monomer units comprise an average of at least 8, at least 9, or at least 10 carbon atoms. In the case of a mixture of indoleamine, it is the arithmetic mean considered here. In the case of a combination of a diamine and a dicarboxylic acid, the arithmetic mean of the number of carbon atoms of the preferred embodiment of the diamine and the dicarboxylic acid must be at least 8, at least 9, or at least 10. An example of a suitable polyamine is PA610 (which can be made from hexamethylenediamine [6 carbon atoms] and sebacic acid [10 carbon atoms], so the average number of carbon atoms in the monomer unit here is 8 ), PA88 (which can be made from octaethylenediamine and 1,8-octanedioic acid), PA8 (which can be made from caprylolactam), PA612, PA810, PA108, PA9, PA613, PA614, PA812, PA128, PA1010, PA10, PA814, PA148, PA1012, PA11, PA1014, PA1212 and PA12. The manufacture of polyamines is prior art. It is of course also possible to use copolyamines which are based on polyamines, where it is also possible to optionally use monomers such as caprolactam.

The polyamine can also be a polyether ester decylamine or a polyether decylamine. Polyether amides are known in principle from, for example, DE-A 30 06 961. It comprises a polyether diamine as a comonomer. Suitable polyether diamines can be reactively aminated via corresponding polyether diols Or obtained by subsequent conversion of the hydrogenation to acrylonitrile (for example EP-A-0 434 244; EP-A-0 296 852). The number average molecular weight thereof is usually from 230 to 4,000; and the polyetheramine content thereof is preferably from 5 to 50% by weight.

Derived from the polyether glycol diamine commercially available from Huntsman, which is a product JEFFAMINE ^® D. The polyether diamine derived from 1,4-butanediol or 1,3-butanediol also has good applicability and has a mixed structure (for example, a disordered or block-like distribution of units derived from a diol) The same is true for polyetheramide.

Mixtures of various polyamines can also be used, with the prerequisites being suitable compatibility. Those skilled in the art are aware of compatible polyamine combinations; combinations that may be listed herein are, for example, PA12/PA1012, PA12/PA1212, PA612/PA12, PA613/PA12, PA1014/PA12, and PA610/PA12, and have PA11 Corresponding combination. In case of doubt, a compatible combination can be determined by routine experimentation.

A preferred embodiment uses from 30 to 99% by weight, particularly preferably from 40 to 98% by weight, particularly preferably from 50 to 96% by weight, of the narrower polyamine, and from 1 to 70% by weight, particularly preferably 2 to 60% by weight, particularly preferably 4 to 50% by weight, of a mixture of polyetheresteramine and/or polyetheramine. Here, polyether decylamine is preferred.

The molding composition may comprise other components together with polyamines such as impact modifiers, other thermoplastics, plasticizers, and other conventional additives. The only requirement is that the polyamine forms a matrix of the molded composition.

An example of a suitable impact modifier is an ethylene/α-olefin copolymer. Best from

a) an ethylene/C ₃ -C ₁₂ -α-olefin copolymer having from 20 to 96, preferably from 25 to 85% by weight of ethylene. The ratio of C ₃ -C ₁₂ -α-olefin used is propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene. Typical examples herein are ethylene-propylene rubber, as well as LLDPE and VLDPE.

b) having from 20 to 96, preferably from 25 to 85% by weight of ethylene and up to about 10% by weight of a non-conjugated diene such as bicyclo [2.2.1] heptadiene, 1.4-hexadiene, dicyclopentane An ethylene/C ₃ -C ₁₂ -α-olefin/non-conjugated diene terpolymer of a diene or 5-ethene norbornene. Suitable C ₃ -C ₁₂ -α-olefins are likewise, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene or 1-dodecene.

The manufacture of such copolymers or terpolymers, for example by the aid of a Ziegler-Natta catalyst, is a prior art.

Other suitable impact modifiers are styrene-ethylene/butylene block copolymers. Here, it is preferred to use a styrene-ethylene/butylene-styrene block copolymer (SEBS) which can be produced by hydrogenation of a styrene-butadiene-styrene block copolymer. However, it is also possible to use a diblock system (SEB) or a multi-block system. Block copolymers of this type are prior art.

The impact modifiers preferably comprise an acid anhydride group which is via a backbone polymer with an unsaturated dicarboxylic anhydride, an unsaturated dicarboxylic acid or not in a conventional manner at a concentration sufficient to be well coupled to the polyamine. A thermal reaction or a radical reaction of a monoalkyl ester of a saturated dicarboxylic acid is introduced. An example of a suitable reagent is butenene. Diacid, maleic anhydride, monobutyl maleate, fumaric acid, citraconic anhydride, aconitic acid or itaconic anhydride. Preferably, 0.1 to 4% by weight of the unsaturated anhydride is grafted to the impact modifier by this method. According to the prior art, the unsaturated dicarboxylic anhydride or its precursor can also be used as a graft together with other unsaturated monomers such as styrene, alpha-methylstyrene or hydrazine.

Other suitable impact modifiers are copolymers comprising units of the following monomers: a) from 20 to 94.5% by weight of one or more alpha-olefins having from 2 to 12 carbon atoms, b) from 5 to 79.5% by weight. One or more acrylic compounds selected from the group consisting of - acrylic acid, methacrylic acid and salts thereof, - an ester of acrylic acid or methacrylic acid with a C ₁ -C ₁₂ alcohol, respectively, wherein the esters optionally have free hydroxyl groups or epoxy groups Functional group, - acrylonitrile or methacrylonitrile, - acrylamide or methacrylamide, c) 0.5 to 50% by weight of olefinically unsaturated epoxide, carboxylic anhydride, formamidine, Oxazoline or ketone.

Such copolymers are described in more detail in WO 2010/094528; the disclosure of which is expressly incorporated herein by reference.

In a preferred embodiment, the polyamine molding composition herein comprises the following components: 1.60 to 96.5 parts by weight of polyamine, 2.3 to 39.5 parts by weight of an impact group containing an acid anhydride group. a component, wherein the impact-resistant component is selected from the group consisting of an ethylene/α-olefin copolymer and a styrene-ethylene/butylene block copolymer, 3. 0.5 to 20 parts by weight of a unit containing the following monomers Copolymer: a) 20 to 94.5 wt% of one or more alpha-olefins having 2 to 12 carbon atoms, b) 5 to 79.5% by weight of one or more acrylic compounds selected from - acrylic acid, methyl Acrylic acid and its salts, - esters of acrylic acid or methacrylic acid with C ₁ -C ₁₂ alcohols, respectively, wherein the ester optionally carries free hydroxyl or epoxy functional groups, - acrylonitrile or methacrylonitrile, - acrylamide or Methyl acrylamide, c) 0.5 to 50% by weight of olefinically unsaturated epoxide, carboxylic anhydride, formamidine, Oxazoline or A ketone wherein the total weight of the components according to items 1, 2 and 3 is 100.

In a preferred embodiment, the molding composition comprises: from 1.65 to 90 parts by weight, particularly preferably from 70 to 85 parts by weight of polyamine, from 2.5 to 30 parts by weight, particularly preferably from 6 to 25. Part by weight, particularly preferably from 7 to 20 parts by weight of the impact-resistant modifying component, from 3.0.6 to 15 parts by weight, particularly preferably from 0.7 to 10 parts by weight, of the copolymer, preferably containing the units of the following monomers: a) 30 to 80% by weight of the α-olefin, b) 7 to 70% by weight, particularly preferably 10 to 60% by weight of the acrylic compound, c) 1 to 40% by weight, particularly preferably 5 to 30% by weight of the olefin Unsaturated epoxide, carboxylic anhydride, formamidine, Oxazoline or ketone.

Other impact-resistant modifying components that may also be used are nitrile rubber (NBR) or hydrogenated nitrile rubber (HNBR), wherein the rubbers optionally contain functional groups. US 2003/0220449 A1 describes a corresponding molded composition.

Other thermoplastics that can be used in the polyimide molding compositions are primarily polyolefins. In one embodiment, an acid anhydride group may be included at an earlier stage of the impact modifier as described above, and then an unfunctionalized impact modifier may be optionally present together. In other embodiments, the impact modifiers are unfunctionalized and are present in a molded composition in combination with a functionalized impact modifier or with a functionalized polyolefin. The term "functionalized" means a group which has been reacted with a terminal group of polyamine according to the prior art, such as an acid anhydride group, a carboxyl group, an epoxy group or Oxazolinyl. The functional composition of the functionalized or unfunctionalized polyolefin, and from 3.1 to 49 parts by weight of the polyfunctional amine, from 0.1 to 49 parts by weight of the functionalized or unfunctionalized polyolefin, and from 3.1 to 49 parts by weight of the functional group. A modified or unfunctionalized impact-resistant modifier wherein 100 parts by weight of the components of items 1, 2 and 3 are 100 parts by weight.

Examples of polyolefins are polyethylene or polypropylene. In principle, any commercial grade may be used. Therefore, examples of users are: high density, medium density Or low density linear polyethylene, LDPE, ethylene-acrylate copolymer, ethylene-vinyl acetate copolymer, homologous or miscellaneous polypropylene, propylene and ethylene mess copolymer and / or 1-butene, An ethylene-propylene block copolymer or the like. The polyolefin can be produced by any known method, for example, by a 戚-nano or Phillips process, or by using a metallocene or by a free radical route. In this case, the polyamine can also be, for example, PA6 and/or PA66.

In a possible embodiment, the molding composition comprises from 1 to 25% by weight of a plasticizer, particularly preferably from 2 to 20% by weight, particularly preferably from 3 to 15% by weight.

Plasticizers and their use with polyamines are known. An overview of plasticizers suitable for polyamines can be found in Gächter/Müller, Kunststoffadditive [Plastics Additives], C. Hanser Verlag, 2nd edition, page 296. Examples of suitable compounds suitable as plasticizers are esters of p-hydroxybenzoic acid having from 2 to 20 carbon atoms in the alcohol component, or guanamines of arylsulfonic acid having from 2 to 12 carbon atoms in the amine component, Preferred is decylamine of benzenesulfonic acid. Plasticizers which can be used are especially ethyl p-hydroxybenzoate, octyl p-hydroxybenzoate, isohexadecyl p-hydroxybenzoate, N-n-octyltoluenesulfonamide, N-n-butyltoluenesulfonamide Or N-2-ethylhexyltoluenesulfonamide.

The molding composition may additionally contain customary amounts of additives which are required to establish specific properties. Examples of such additives are pigments or fillers (such as carbon black, titanium dioxide, zinc sulfide), silicate or carbonate reinforced fibers (such as glass fibers), processing aids (such as wax, zinc stearate or calcium stearate). ), a flame retardant (such as magnesium hydroxide, aluminum hydroxide or cyanide) Acid melamine), an antioxidant, a UV stabilizer, a hydrolyzing stabilizer, and an additive that imparts antistatic properties or electrical conductivity to the product (eg, carbon fiber, graphite fibrils, stainless steel fibers, or conductive carbon black). The polyamide molding composition preferably contains 0.01 to 3% by weight of carbon black to improve UV resistance, and contains a biocide to inhibit molluscs and other marine life from colonizing.

When the applied polyamine molding composition has a viscosity at 240 ° C and a shear rate of 0.1 1 / s, the viscosity is at least 2000 Pa. s, preferably at least 2300 Pa. s, more preferably at least 3000 Pa. s, especially good for at least 5000 Pa. s, and the best is at least 8000 Pa. In particular, the polyamide sheath has good mechanical robustness. Viscosity is determined by a cone cone viscometer according to ASTM D4440-3.

The high viscosity of the polyamide molding composition is usually accompanied by the high molecular weight of the polyamide. The solution viscosity is a measure of the molecular weight of the polyamine. For the purposes of the present invention, it is preferred that the polyamidamide in the molding composition applied has a relative solution viscosity η _rel of at least 1.5, more preferably at least 1.8, particularly preferably at least 2.0, and most preferably at least 2.2. It was measured according to ISO 307 at 23 ° C in a 0.5% by weight solution in m-cresol.

A known method for making this type of polyamine is solid phase post condensation of pelletized low viscosity polyamine to produce a high viscosity polyamine at temperatures below the melting point. This method is described, for example, in CH 359 286 and US 3 821 171. The solid phase post condensation of polyamine is usually carried out in a batch or continuously operated dryer under inert gas or vacuum. This method enables the production of polyamines having a very high molecular weight.

Another method of making high viscosity polyamines is to use a variety of different screw-based equipment for continuous post-condensation of the melt.

WO 2006/079890 states that a high viscosity polyamine molding composition can be obtained by mixing a high molecular weight polyamine with a low molecular weight polyamine.

Other possible ways to obtain high viscosity polyamine or high viscosity polyamine molding compositions are to use molecular weight increasing additives; suitable additives and/or methods are described, for example, in the following specification: WO 98/47940, WO 96/34909 , WO 01/66633, WO 03/066704, JP-A-01/197526, JP-A-01/236238, DE-B-24 58 733, EP-A-1 329 481, EP-A-1 518 901 EP-A-1 512 710, EP-A-1 690 889, EP-A-1 690 890 and WO 00/66650.

However, at high pressures at the die, molding compositions made according to this prior art typically require very high current draw or very high torque during the extrusion process. In addition, high shear forces cause significant chain splitting and thus lower molecular weight during processing.

Accordingly, for the purposes of the present invention, it is preferred that the condensation process to increase the molecular weight of the polyamide molding composition by means of an increase in molecular weight additive is delayed until the beginning of the treatment process. Accordingly, the present invention also contemplates the use of the claimed claim that the extruded layer made of the polyamide composition has been applied by the following processing steps: a) providing a polyimide molding composition, b) making a premix of the polyamine molding composition with an increase in molecular weight additive (for example a compound having at least two carbonate ester units), c) storing and/or transporting the mixture, if appropriate, d) The mixture is used in an extrusion process in which the molecular weight is increased The condensation process is delayed until the extrusion process begins.

It has been found that the use of this additive mode during processing results in a significant increase in melt stiffness, while the load on the motor is simultaneously reduced. Therefore, even if the melt viscosity is high, high processing yield may be obtained, and as a result, the cost efficiency of the manufacturing method is improved. The process is described below in the context of, for example, a compound having an increased molecular weight as a compound having at least two carbonate units.

The molecular weight M _{n of the} starting polyamine is preferably greater than 5,000, in particular greater than 8,000. The polyamine used herein is one in which the terminal group has an amine group at least to some extent. For example, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the end groups are in the form of an amine end group. The use of diamines or polyamines as chain transfer agents to make polyamines having relatively high amine end groups is a prior art. In the present example, it is preferred to use an aliphatic, cycloaliphatic or araliphatic diamine having 4 to 44 carbon atoms as a chain transfer agent to produce the polyamine. Examples of suitable diamines are hexamethylenediamine, decethylenediamine, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, dodecylenediamine, 1,4 -diaminocyclohexane, 1,4- or 1,3-dimethylaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4'-diamino-3, 3'-Dimethyldicyclohexylmethane, 4,4'-diaminodicyclohexylpropane, isophoronediamine, meta-xylylenediamine or p-xylylenediamine.

In other preferred embodiments, polyamines are used as chain transfer agents during the manufacture of polyamines and as a branching agent. Examples here are diethylenetriamine, 1,5-diamino-3-(β-aminoethyl)pentane, ginseng (2-aminoethyl)amine ,N,N-bis(2-Aminoethyl)-N',N'-bis[2-[bis(2-aminoethyl)amino]ethyl]-1,2-ethanediamine, dendrimer Polymers, and polyethyleneimine, especially branched polyethyleneimine, which can be obtained by polymerization of anthracycline (Houben-Weyl, Methoden der Organischen Chemie [Methods of organic chemistry], Vol. E20, No. 1482- Page 1487, Georg Thieme Verlag Stuttgart, 1987), and typically has the following amine group distribution: 25 to 46% of the amine group, 30 to 45% of the secondary amine group, and 16 to 40% of the tertiary amine group.

The proportion of the compound having at least two carbonate units is from 0.005 to 10% by weight, which is calculated as a ratio relative to the polyamine used. The ratio is preferably in the range of 0.01 to 5.0% by weight, particularly preferably in the range of 0.05 to 3% by weight. The term "carbonate" as used herein means an ester of carbonic acid, particularly with a phenol or with an alcohol.

The compound having at least two carbonate units may be a low molecular weight or oligomeric or polymeric compound. It may consist entirely of carbonate units or may have other units. These are preferably oligomeric or polyamido units, oligomeric or polyester units, oligomeric or polyether units, oligomeric or polyetheresteramine units, or oligomeric or polyetherimide units. These compounds can be produced by known oligomerization or polymerization methods, or by polymer-analog reactions.

In a preferred embodiment, the compound having at least two carbonate units is a polycarbonate, such as a polycarbonate based on bisphenol A, or a block copolymer containing such polycarbonate blocks.

When the compound used as an additive and having at least two carbonate units is metered in the form of a masterbatch, the amount of the additive can be more accurately measured due to the larger amount. It has also been found that the use of masterbatch additives improves the quality of the extrudate. The masterbatch preferably comprises a polyamine which has a molecular weight which is also improved by the condensation process of the present invention, or a polyamine which is compatible therewith but which is incompatible under the reaction conditions and which has a molecular weight increased by a condensation process. Partial linkages may also occur between them and this results in a compatible polyamine as a matrix material. The molecular weight M _n of the polyamine used as the matrix material in the masterbatch is preferably greater than 5,000, in particular greater than 8,000. Preferred are polyamipenides having a terminal group predominantly in the form of a carboxylic acid group. For example, at least 80%, at least 90%, or at least 95% of the end groups are in acid form. Alternatively, it is possible to use polyamines whose terminal groups are predominantly amine groups; this process results in improved hydrolysis resistance.

The concentration of the compound having at least two carbonate units in the master batch is preferably from 0.15 to 50% by weight, particularly preferably from 0.2 to 25% by weight, particularly preferably from 0.3 to 15% by weight. Masterbatches of this type are made by conventional methods known to those skilled in the art.

Suitable compounds having at least two carbonate units and suitable masterbatch are described in detail in WO 00/66650, which is incorporated herein by reference in its entirety.

The present invention may be used in combination with at least 5 ppm of polyphosphorus in the form of an acidic compound in the form of a process. In this case, a salt of a weak acid of from 0.001 to 10% by weight, based on the polyamine, is added to the polyamine prior to the batching process or during the batching process. DE-A 103 37 707 discloses suitable salts, which are incorporated herein by reference.

However, the present invention has less than 5 ppm due to process limitations. Phosphorus or phosphorus-free polyamines in the form of acidic compounds are equally good applicability. Although a salt of a corresponding weak acid may be added in this example, it is not necessarily necessary to add it.

The compound having at least two carbonate units is added in the original state or in the form of a masterbatch until after the batching process (i.e., after the production of the polyamide molding composition but at least during the treatment). Preferably, during the treatment, the polyamine or the polyamine molding composition whose molecular weight is increased by the condensation process is a pellet and a pellet of a compound having at least two carbonate units. Or powder mix or mix with the corresponding masterbatch. However, it is also possible to manufacture pellets of the finished polyamine molding composition with a compound having at least two carbonate units or with a masterbatch, and then transport or store it before being treated. It is naturally also possible to use a powder mixture in the corresponding operation. The decisive factor is that the mixture does not melt until the start of the treatment. It is recommended to thoroughly mix the melt during the treatment. However, it is also possible to meter the masterbatch in the form of a melt stream into the melt of the polyamine molding composition to be treated by means of an auxiliary extruder and then combine by thorough mixing; in this case In the process, steps b) and (d) are combined.

It is also possible to use any other suitable molecular weight increasing additive in place of a compound having at least two carbonate units, such as the additives disclosed in the above references. Here again, a suitable amount ratio is from 0.005 to 10% by weight (this ratio is calculated relative to the polyamine used), preferably from 0.01 to 5.0% by weight, particularly preferably from 0.05 to 3% by weight.

The thickness of the layer of polyamine applied must be at least sufficient to produce the bonding layer under the conditions of the application process. Preferably, the layer has a thickness of at least 0.5 mm, Do not be at least 1.0 mm, and at least at least 1.2 mm.

Successful bar thicknesses have generally proven to be up to about 8 mm, preferably up to about 7 mm, particularly preferably up to about 6 mm, and particularly preferably up to about 5 mm. However, if necessary, it is also possible to selectively thicker layers, for example up to 30 mm or more.

The polyamide layer can be applied directly to the metal surface. In this case, it is advantageous that the polyamine molding composition comprises an adhesive resin such as an epoxy resin (for example, Araldite ^® ). However, there is typically at least an additional layer between the metal surface and the polyamide layer. The layers referred to herein may be, for example, the following: - a ceramic layer, for example according to WO 03/093374; - an undercoat layer, for example made of an epoxy resin (US 5 580 659) or an epoxy resin with a polyacrylate latex The water is made of a mixture of substrates (WO 00/04106); - an adhesion promoter layer made of a hot melt polyamine adhesive, which can be applied as a powder, for example by spraying or the like (EP 1 808 468 A2 ) or made of a polyolefin with a functional group. The functional group which can be used is, for example, a carboxyl group or an acid anhydride group (WO 02/094922), an epoxy group or an alkoxyalkyl group (EP-A-0 346 101). The polyolefin layer can also be foamed. The polyolefin is preferably polyethylene or polypropylene; - an adhesion promoter having different compositions for the purpose of ensuring that mechanical stress is not impaired and the bond between the polyamide layer and the underlying material; - textile reinforcement in the form of a woven or mat The material is made, for example, of glass fiber or aramid fiber (Kevlar).

The following layer configurations are preferred: metal/ceramic layer/polyamide layer; metal/ceramic layer/primer/polyamine layer; metal/ceramic layer/primer/adhesion promoter/polyamide layer; metal / undercoat / polyamide layer; metal / undercoat / adhesion promoter / polyamide layer; metal / primer / polyolefin layer / polyamide layer; metal / primer / adhesion promoter / Polyolefin layer / polyamide layer; metal / undercoat / adhesion promoter / polyolefin layer / adhesion promoter / polyamine layer; metal / adhesion promoter / polyamide layer.

Any desired method can be used to apply a possible ceramic layer, primer layer and/or polyolefin layer to the tube. A suitable method is the prior art.

The polyamide layer is applied according to known methods, for example by extrusion or extrusion coating. In a possible variant, the polyamide layer is produced and applied together with the same polyolefin layer or adhesion promoter layer to be applied via co-extrusion of the multilayer composite.

Extrusion tube method or extrusion coating method is a method that has been successfully applied to the tube with a protective layer for a long time. This method is described in more detail in Stahlrohr-Handbuch [Steel tube handbook], 12th edition, pages 392-409, Vulkan-Verlag Essen, 1995.

The outer diameter of the metal tube is preferably at least 20 mm and at most 7000 mm.

The individual tubing are structurally bonded to each other in a known manner, for example via welding.

The present invention is applied because the applied polyamide layer has high mechanical strength, good abrasion resistance, very high scratch resistance, good adhesion, and optimized thickness and excellent resistance to seawater and atmospheric influences. It ensures good corrosion protection and good protection against mechanical effects.

The invention also proposes the use of the obtained basic structure for the use of offshore structures in the claimed right, for example for offshore wind energy systems. Since the extrusion coating method greatly reduces the degree of coating of the crucible, the characteristics of the basic structure of the present invention are more significantly prolonged in service life than the prior art structure.

Claims (10)

A use of a steel tube with a sheath formed from an extruded layer of a polyamide molding composition for use in incorporating a foundation structure of an offshore structure. For example, the application of the scope of claim 1 wherein the offshore structure is an offshore wind energy system, a drilling platform or a lighthouse. The use of the first aspect of the patent application, wherein the extruded layer is composed of a polyamide molding composition having a thickness of 0.5 to 30 mm. The use of claim 1, wherein one or more of the group consisting of: the metal tube and the layer made of the polyamide composition are present in one or more of the group consisting of: - Ceramic layer - undercoat - adhesion promoter layer and - textile reinforcement in the form of a woven or felt. The use of the first aspect of the patent application, wherein the extruded polyamine molding composition has a viscosity of 240 ° C and a shear rate of 0.1 1 / s at a rate of at least 2000 Pa according to ASTM D4440-3. s. The use of the first aspect of the invention, wherein the polyamidamide in the extruded molding composition has a relative solution viscosity η _rel of at least 1.5 according to ISO 307. The use of the first aspect of the invention, wherein the extruded layer made of the polyamide molding composition has been applied by the following processing steps: a) providing a polyamide molding composition, b) preparing a premix of the polyamide molding composition and an additive for increasing the molecular weight, c) storing and/or transporting the mixture if appropriate, d) then applying the mixture to an extrusion process, wherein the molecular weight is increased The condensation process is delayed until the extrusion process begins. The use of the first aspect of the invention, wherein the molecular weight increasing additive is a compound having at least two carbonate units. For example, the application of the scope of claim 2, wherein the offshore structure is an offshore wind energy system, and the basic structure is a single pile (monopile), a sleeve type pile, a tripod base (tripod), a tripod base. Pile (quadropod) or triple pile (tripile). An infrastructure of an offshore structure made according to the use of any of the aforementioned patent claims.